14 Feb 2022
14 Feb 2022
Status: this preprint is currently under review for the journal CP.

Glacial state of the global carbon cycle: time-slice simulations for the last glacial maximum with an Earth-system model

Takasumi Kurahashi-Nakamura, André Paul, Ute Merkel, and Michael Schulz Takasumi Kurahashi-Nakamura et al.
  • MARUM - Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Bremen, Germany

Abstract. Three time-slice carbon-cycle simulations for the last glacial maximum (LGM) constrained by the CO2 concentration in the atmosphere and the amount of carbon stored in the deep ocean were carried out with a fully-coupled comprehensive climate model CESM1.2 (the Community Earth System Model version 1.2). Although the three modeled LGM ocean states had remarkably different physical features, all of them were compatible with the pre-industrial (PI) state in terms of the global ocean carbon inventory considering the presumed transfers of carbon among the various reservoirs during the evolution from the LGM to PI. The increase in the total alkalinity required to simulate ocean states that is deemed appropriate for the LGM was quantitatively in line with the scenario of post-glacial shallow water deposition of calcium carbonate, suggesting that the reconstructed estimates of the glacial deep-ocean carbon inventory and those of the amount of carbonate deposition on shelves are in agreement with each other. On the other hand, comparisons between the simulated distributions of paleoceanographic tracers and corresponding reconstructions clearly distinguished the different geometry of ocean-circulation cells and favored a shallower Atlantic meridional overturning circulation (AMOC) for the LGM compared to PI.

Takasumi Kurahashi-Nakamura et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on cp-2022-8', Peter Köhler, 18 Feb 2022
    • AC1: 'Reply on CC1', Takasumi Kurahashi-Nakamura, 23 Feb 2022
  • RC1: 'Comment on cp-2022-8', Anonymous Referee #1, 16 Mar 2022
  • RC2: 'Comment on cp-2022-8', Anonymous Referee #2, 18 Mar 2022

Takasumi Kurahashi-Nakamura et al.

Takasumi Kurahashi-Nakamura et al.


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Short summary
With a comprehensive Earth-system model including the global carbon cycle, we simulated the climate state during the last glacial maximum. We demonstrated that the CO2 concentration in the atmosphere both in the modern (pre-industrial) age (~280 ppm) and in the glacial age (~190 ppm) can be reproduced by the model with a common configuration by giving reasonable model forcing and total ocean inventories of carbon and other biogeochemical matter for the respective ages.